# RACING MATH FORMULA'S

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### CAR MATH FORMULA'S

Here are the formulas for most of the Car Math Calculators used on this site as well as a few additional ones that are not on the site. NOTES N1) Many of the formulas use the value of pi which is 3.1415927 N2) Some formulas contain notation such as ^2 which means "squared"
Formulas for displacement, bore and stroke pi/4 = 0.7853982 cylinder volume = pi/4 x bore^2 x stroke stroke = displacement / (pi/4 x bore^2 x number of cylinder.
Formulas for compression ratio (CylVolume + ChamberVolume) / ChamberVolume cylinder volume = pi/4 x bore^2 x stroke chamber volume = cylinder volume / compression ratio - 1.0 displacement ratio = cylinder volume / chamber volume amount to mill = (new disp. ratio - old disp. ratio / new disp. ratio x old disp. ratio) x stroke
Formulas for piston speed piston speed in fpm = stroke in inches x rpm / 6 rpm = piston speed in fpm x 6 / stroke in inches
Formulas for brake horsepower horsepower = rpm x torque / 5252 torque = 5252 x horsepower / rpm brake specific fuel consumption = fuel pounds per hour / brake horsepower bhp loss = elevation in feet / 1000 x 0.03 x bhp at sea level
Formulas for indicated horsepower & torque horsepower = mep x displcement x rpm / 792,00 torque = mep x displacement / 150.8 mep = hp x 792,000 / displacement x rpm mep = hp x 792,000 / displacement x rpm mechanical efficiency = brake output / indocated output x 100 friction output = indicated output - brake output taxable horsepower = bore2 x cylinders / 2.5
Formulas for air capacity & volumetric efficiency theoretical cfm = rpm x displacement / 3456 volumetric efficiency = acutal cfm / theoretical cfm x 100 street carb cfm = rpm x displacement / 3456 x 0.85 racin carb cfm = rpm x displacement / 3456 x 1.1
Formulas for tire size & their effect tire diameter = 2 x selection width x aspect ratio / 2540 + rim diameter effective ratio = old tire diameter / new tire diameter x original ratio actual mph = new tire diameter / old tire diameter x actual mph
Formulas for g force & weight transfer drive wheel torque = flywheel torque x first gear x final drive x 0.85 wheel thrust = drive wheel torque / rolling radius g = wheel thrust / weight weight transfer = weight x cg height / wheelbase x g lateral acceleration = 1.227 x raduis / time^2 lateral weight transfer = weight x cg height / wheel track x g centrufugal force = weight x g Formulas for shift points rpm after shift = ratio shift into / ratio shift from x rpm before shift drivehsaft torque = flywheel torque x transmission ratio
Formula for instrument error actual mph = 3600 / seconds per mile speedo error percent = difference between actual and indicated speed / actual speed x 100 indicated distance = odometer reading at finish - odometer reading at start odo error percent = difference between actual and indicated distances / actual distance x 100
Formulas for MPH RPM gears & tires mph = rpm x tire diameter / gear ratio x 336 rpm = mph x gear ratio x 336 / tire daimeter gear ratio = rpm x tire diameter / mph x 336 tire diameter = mph x gear ratio x 336 / rpm
Formulas for weight distribution percent of weight on wheels = weight on wheels / overweight x 100 increased weight on wheels = [ distance of cg from wheels / wheelbase x weight ] + weight
Formulas for center of gravity cj location behind front wheels = rear wheel weights / overall weight x wheelbase cg location off-center to heavy side = track / 2 - [ weight on light side / overall weight ] x track cg height = [ level wheelbase x raised wheelbase x added weight on scale / distance raised ] x overall weight